Clinics in diagnostic imaging (217).

A 54-year-old woman, with a past medical history of hyperthyroidism and endometriosis (laparoscopic cystectomy was performed in 2003 and 2006), underwent routine health screening blood tests. She was found to have elevated CA125 at 266 (reference range 0–35) kU/L and CA19-9 at 165 (reference range <34.1) U/mL. She was referred by a private practitioner for positron emission tomography/computed tomography (PET/CT) [ Figure 1 ] and, subsequently, magnetic resonance imaging (MRI) of the pelvis [ Figure 2 ]. What do these images show? What is the diagnosis? (a) Axial unenhanced CT and (b) PET fusion images of the pelvis. (a) Axial T2-W, (b) sagittal T2-W, (c) axial diffusion-weighted (b-1000) and (d) apparent diffusion coefficient map MR images of the pelvis.

The axial unenhanced CT image of the pelvis [ Figure 1a ] shows a mass in the left pouch of Douglas (arrow) inseparable from the posterior uterine myometrium and the adjacent rectosigmoid colon. The PET fusion image of the pelvis [ Figure 1b ] shows a 18 F-fluorodeoxyglucose (FDG)-avid mass (arrow) with a focus of FDG activity in the posterior myometrium (arrowhead). Axial T2-weighted (T2-W) [ Figure 2a ] and sagittal T2-W [ Figure 2b ] MR images of the pelvis show a large adenomyoma in the posterior myometrium (arrowhead). Within it, there are multiple poorly demarcated T2-W intermediate signal lesions, one of which is extending into the left pouch of Douglas (arrow) and abuts the adjacent rectosigmoid colon. These lesions are hyperintense on diffusion-weighted image (DWI; b-1000) [arrow in Figure 2c ] and hypointense on apparent diffusion coefficient (ADC) map [arrow in Figure 2d ], indicating restricted diffusion, which is suspicious for malignancy. The endometrium [dashed arrow in Figure 2a ] and bilateral ovaries are normal (not depicted in the figure).

The patient underwent total hysterectomy and bilateral salpingo-oophorectomy, with dissection of the paraaortic and pelvic lymph nodes, infragastric omentectomy and anterior resection of the sigmoid colon. The histology of the tumour showed endometrioid adenocarcinoma grade 3 arising from adenomyosis within the posterior myometrium, invading the muscularis propria of the sigmoid colon and mesocolon. Metastatic deposits were identified in three of the pericolic lymph nodes. The rest of the pelvic and paraaortic lymph nodes, as well as the omentum and appendix were free of disease. She completed adjuvant chemotherapy (six cycles of paclitaxel and carboplatin) followed by radiotherapy. At the one-year follow-up, the patient was disease free.

Endometrial carcinoma arising from adenomyosis (EC-AIA).

Endometrial cancer arising from adenomyosis or adenomyotic foci is a rare entity. A literature review by Habiba et al .[ 1 ] in 2018 identified 78 case reports that describe EC-AIA between the years 1897 and 2017. A case series by Mao et al .[ 2 ] in 2017 reported the malignant transformation rate of adenomyosis at 2.4%. There are no specific symptoms or signs in EC-AIA, especially at an early stage.[ 2 ] As there is no communication between the mass and the endometrial cavity, patients do not typically present with abnormal uterine bleeding as one with endometrial cancer would. The patients may present with pelvic discomfort, pelvic mass effect or elevated serum biomarkers. In our case, the patient was found to have elevated tumour markers on health screening and she was asymptomatic. Colman and Rosenthal[ 3 ] proposed the following criteria for the diagnosis of EC-AIA: (a) absence of cancer in the eutopic endometrium; (b) cancer arising from adenomyosis and not due to invasion from other primary cancers; and (c) presence of adenomyosis as evidenced by surrounding endometrial stromal cells.[ 3 , 4 ] The modality of choice for the locoregional staging of gynaecological malignancies is MRI. In addition, MRI is useful for preoperative planning and postoperative adjuvant radiotherapy planning. The excellent tissue contrast of MRI allows detection of tumour infiltration into the surrounding pelvic structures. The combination of T2-W and dynamic contrast-enhanced images has high accuracy for endometrial cancer staging.[ 5 ] Malignancies have higher cellular density than normal tissue or benign tumours. Thus, DWI and ADC map have high sensitivity and specificity in distinguishing malignancies from benign tumours. Malignant neoplasm, particularly high-grade tumour, has significantly lower ADC value than benign neoplasm.[ 6 ] Apart from detection of primary tumour with high accuracy, PET/CT is also useful for detection of nodal disease or distant metastases.[ 7 ] It has high specificity in detecting pathological nodes and metastatic deposits.[ 5 , 7 , 8 ] It is shown that PET/CT has greater accuracy in nodal disease detection than MRI.[ 8 ] However, the sensitivity is size dependent. The detection rate is 100% for a metastatic deposit size of ≥10 mm but drops significantly if it is <10 mm, resulting in high false-negative rate.[ 5 , 8 ] Our patient had pericolonic nodal metastasis, but this was discernible neither on PET/CT nor MRI, probably due to the small size of the metastatic deposit. A literature search by Izumi et al .[ 9 ] in 2020 revealed less than ten cases of MRI findings of EC-AIA. These MRI findings were classified into the following three patterns: (a) thickened myometrium with poorly demarcated T2-W hyperintense areas, (b) well-circumscribed T2-W mildly hyperintense mass within the myometrium, and (c) subserosal T1-W and T2-W hyperintense cystic mass (cystic adenomyosis) that contains internal solid papillary projections or nodules (these solid components show contrast enhancement and restricted diffusion). Our case would fit the first classification, where poorly demarcated T2-W intermediate signal foci are present within the posterior myometrium in the background of adenomyosis. The exophytic mass in the left pouch of Douglas represents extrauterine extension of the cancer. In view of previous history of endometriosis, a synchronous cancer arising in extraovarian endometriosis would be a plausible differential diagnosis for the mass in the pouch of Douglas. Endometriosis-associated malignancy is a rare condition that is seen in approximately 1% of women with endometriosis. Extraovarian sites constitute 25% of endometriosis-associated malignancies. The typical MRI findings of cancer arising in extraovarian endometriosis include solid lesion with intermediate signal intensity on T1-weighted (T1-W) and T2-W images, demonstrating contrast enhancement and restricted diffusion.[ 10 , 11 ] Adenomyosis/adenomyoma and uterine fibroid are common benign gynaecological diseases. Differentiating these diseases on MRI is not difficult. Adenomyosis occurs due to the presence of ectopic endometrial glands and stroma within the uterine myometrium and smooth muscles.[ 1 , 2 ] An adenomyoma is a focal, localised and circumscribed form of adenomyosis, which may appear as a mass in the myometrium. It is typically hypointense on T2-W sequence and contains small, hyperintense foci that represent ectopic endometrial tissues. These foci may be hyperintense on T1-W, which represent blood product.[ 12 ] Adenomyosis/adenomyoma can act as a precursor for endometrial cancer.[ 1 ] They commonly coexist with endometrial cancer, especially endometrioid endometrial cancer histotype. The coexistence of adenomyosis and endometrial cancer was found in 16%–34% of hysterectomy specimens for treatment of endometrial cancer.[ 13 ] Machida et al defined coexistence of endometrial cancer and adenomyosis as the concurrent presence of adenomyosis accompanied by endometrial cancer in the endometrium.[ 4 ] A leiomyoma is a myometrial mass that consists of predominantly smooth muscle cells separated by fibrous connective tissues. On MRI, a classic leiomyoma is typically well demarcated and homogeneously hypointense on T2-W sequence.[ 14 ] As opposed to a leiomyoma, an adenomyoma is more elliptical and has less-circumscribed margin, less mass effect and no tortuous vessels along its margin [ Figure 3 ].[ 12 ] A 45-year-old woman with leiomyoma and adenomyoma. (a) Sagittal and (b) axial T2-W MR images of the pelvis show a classic leiomyoma in the anterior wall (arrow), which is hypointense and has a well-circumscribed margin. As opposed to the leiomyoma, the adenomyoma in the posterior fundal wall (*) is less hypointense on T2-W image, and has an ill-circumscribed margin and multiple tiny T2-W hyperintense foci within. (c) On axial T1-W MR image, these foci are hyperintense (arrowhead), representing blood product. (d) Contrast-enhanced sagittal T1-W MR image shows the adenomyoma (*) with contrast enhancement similar to the rest of the myometrium, while the leiomyoma (arrow) shows mild heterogeneous enhancement. Leiomyomas show variable contrast enhancement. The second differential diagnosis for this case would be a leiomyosarcoma arising from an existing fibroid with extrauterine extension. Leiomyosarcoma typically presents as a large, irregular, ill-defined and infiltrating myometrial mass that shows rapid growth. On T1-W images, it is heterogeneously hypointense and may show hyperintense areas, which are attributed to haemorrhage. On T2-W images, it is intermediate to hyperintense. The hyperintense areas on T2-W images represent internal necrosis. The solid component of the leiomyosarcoma demonstrates early avid contrast enhancement. Leiomyosarcoma typically shows restricted diffusion, in which it is hyperintense on DWI and hypointense on ADC map.[ 15 ] The ADC value of leiomyosarcoma is generally lower than that of degenerative and cellular leiomyomas. Thus, the ADC map is useful in differentiating leiomyosarcomas from degenerative and cellular leiomyomas.[ 16 ] Figure 4 shows a case of leiomyosarcoma arising from an existing fibroid. Malignant transformation of uterine fibroid is also a very rare entity. In 2010, Yanai et al .[ 17 ] reported four cases of leiomyosarcoma originating from leiomyoma, and their literature review of leiomyosarcoma originating from leiomyoma from the year 1968 to 2010 revealed only six cases thus far. An 80-year-old woman presented with right soleal vein thrombosis and pelvic mass. (a) Sagittal T2-W MR image of the pelvis shows a large leiomyoma in the uterine fundus (arrow). The upper half of the leiomyoma is T2-W hyperintense and slightly heterogeneous (*). The upper half of the leiomyoma shows heterogeneous avid early contrast enhancement on (b) contrast-enhanced sagittal T1-W MR image, and is hyperintense on (c) diffusion-weighted image (b-1000) (*) and hypointense on (d) apparent diffusion coefficient map (*), in keeping with restricted diffusion. This is proven to be leiomyosarcoma arising from a fibroid on histology. Another reasonable differential diagnosis for our case is primary sigmoid cancer with uterine invasion, given that it is a more common cancer compared to the aforementioned differential diagnoses. The typical imaging features of primary sigmoid cancer include a discrete soft tissue mass, focal colonic mural thickening or circumferential asymmetrical nodular thickening of the colonic wall, which results in luminal narrowing. For locally advanced tumour, there would be infiltration and stranding of the pericolic fat.[ 18 ] However, these features were not present in our case. In our patient, the mass in the left pouch of Douglas caused local mass effect, abutted and displaced the sigmoid colon. The epicentre of the disease was not the sigmoid colon. There was neither circumferential irregular mural thickening of the sigmoid colon nor pericolic fat stranding. Thus, this differential was deemed the least likely. The absence of enlarged locoregional nodes is not a reliable exclusion criterion. The incidence of nodal metastasis in early colon cancer is low, and the incidence rises with advancing stage. In general, lymph node size >1 cm is considered pathological and suspicious for metastasis. However, normal-sized lymph node may harbour microscopic metastasis.[ 18 , 19 ] The same principle can be applied to nodal metastasis in other malignancies. Although difficult, it is possible for radiologists to arrive at the diagnosis if there are typical imaging features. The lesion in our case shows features highly suspicious for malignancy on both MRI and PET/CT. The PET/CT shows an FDG-avid mass in the left pouch of Douglas, which involves the uterus and abuts the sigmoid colon. The MRI pelvis shows abnormal T2-W signal lesions within focal adenomyosis in the posterior myometrium, which extend into the pouch of Douglas. The abnormal foci show restricted diffusion. The constellation of findings are compatible with the first pattern of classification by Izumi et al .[ 9 ] The other differential diagnoses are less likely. In summary, EC-AIA is a rare entity. However, a good understanding of the imaging features of differentials for myometrial masses could aid the preoperative diagnosis. Nil. There are no conflicts of interest.