Imaging features of mucinous carcinoma arising from mature teratoma showing cytokeratin 7+ and cytokeratin 20+ expression profile: A case report

Abstract

Ovarian mature teratomas are benign, but malignant transformation can occur infrequently, especially in women of advanced age. The tissue that undergoes malignant change is mostly squamous cell carcinoma, although adenocarcinoma has been reported in a small number of cases. The immunostaining results of adenocarcinoma usually show a cytokeratin (CK)7-/CK20+ expression profile, corresponding to lower gastrointestinal tract origin. In this report, we describe a case of mucinous carcinoma arising from an ovarian mature teratoma showing a CK7+/CK20+ profile and discuss its imaging features. A 40-year-old woman presented to her primary care physician with abdominal distension and poor oral intake, and she was referred to our hospital. She had been diagnosed with an ovarian mature teratoma at our institution 3 years earlier. At the current presentation, pelvic magnetic resonance imaging showed a large multilocular cystic mass with adipose tissue extending into the upper abdomen. Densely packed cysts were observed inside the mass, which showed weak contrast enhancement on contrast-enhanced imaging and a mildly high signal on diffusion-weighted imaging. A portion of the cysts also showed abnormal 18F-fluorodeoxyglucose uptake (maximum standardized uptake value, 13.2) on positron emission tomography/computed tomography. The patient was subsequently diagnosed with mucinous carcinoma showing a CK7+/CK20+ profile arising from a mature teratoma by pathologic examination. This mucinous carcinoma arising from a mature teratoma showed a CK7+/CK20+ profile and took the form of densely packed multilocular cysts. In this respect, it was similar to primary ovarian epithelial mucinous carcinoma on both magnetic resonance imaging and pathologic examination despite showing a much higher maximum standardized uptake value than that of primary ovarian mucinous carcinoma. When a large ovarian teratoma contains a large multilocular cyst, the presence of densely packed multilocular cysts should not be missed even in a mass without solid components. Clinicians should consider the possibility of mucinous carcinoma showing a CK7+/CK20+ profile arising from a mature teratoma in such cases.

Keywords: Adenocarcinoma; MRI; Mucinous; Ovary; PET-CT scan; Teratoma.

Fig. 1

Pelvic MRI performed 3 years before the current presentation. (A) Axial T1-weighted imaging (TR/TE, 100/4 ms) showed a 5-cm multicystic lesion with high signal intensity in the left ovary (arrow). (B) Axial subtraction image showed that the lesion contained no substantial components except for a 7-mm nodule that appeared to be Rokitansky protuberance (arrow).

Fig. 2

Pelvic MRI. (A) A multicystic lesion occupying the abdominal cavity was shown on axial T1-weighted imaging (gradient echo; TR/TE, 7/4.6 ms). A portion of the cyst showing a high signal (arrow) was suppressed on (B) fat-suppressed T1-weighted imaging (gradient echo; TR/TE, 5/0 ms), corresponding to a fat component (arrow). (C) Axial T2-weighted imaging (TR/TE, 4897/100 ms) showed a dense cystic mass in a portion of the lesion (arrow). (D) The dense cystic portion showed slight contrast enhancement on axial subtraction images (arrow).

Fig. 3

Pelvic MRI and FDG-PET/CT. (A) The dense cystic portion showed a slightly high signal on a diffusion-enhanced image (b = 1000 s/mm²; TR/TE, 6255/78 ms) (arrow). (B) On whole-body FDG PET/CT, high FDG uptake (SUVmax, 13.2) was observed in correspondence with the dense cystic portion (arrow).

Fig. 4

Pathology (hematoxylin and eosin staining). (A) The teratoma lumen, composed of squamous epithelium with hair (thin arrow) and sebaceous glands (arrow), was seen adjacent to the mucous cavity (stars). (B) The mucous cavities consisted of 1 layer of high columnar (mucous) epithelium, corresponding to mucinous adenoma. (C) A part of the mucus cavity consisted of densely packed atypical cells, corresponding to mucinous carcinoma.