IMG_1525.jpg
IMG_1524.jpg
48 year-old female with complaints of abdominal distension for 3 months. CECT revealed large multiloculated cystic lesion in left adnexa measuring 18.1x14.7x12.6cm and other lesions in the right adnexa and Pouch of Douglas. Trucut biopsy reported as malignant epithelial neoplasm from outside and neoadjuvant chemotherapy was given. Serial imaging showed a persistent multiloculated lesion in left adnexa, with intact capsule measuring 25 x 20 x 17cm.So underwent interval cytoreductive TAH+RSO+ Left ovarian tumor excision with omentectomy and pelvic peritonectomy. Section from left ovary. TWO slides A & B.
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ovarian teratoma thymic tissue thymoma Hassall corpuscle
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ovarian mature teratoma thymoma-like neoplasm
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primary ovarian thymoma
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ovarian tumor Hassall corpuscles thymic tissue teratoma small round blue cells histology diagnosis
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Histopathological Analysis - Two Slides from Left Ovarian Tumor (Post-Neoadjuvant Chemotherapy)
Slide A (IMG_1525) - Key Findings:
The most striking and diagnostic feature is the presence of classic Hassall's corpuscles - concentrically laminated, keratinizing epithelial whorls with central eosinophilic/hyalinized debris. Two to three well-formed Hassall's corpuscles are clearly visible, surrounded by:
- A biphasic population: large epithelial/squamoid cells forming the whorled nests, and a dense background of small lymphocytes
- Loose myxoid/fibrillary stroma with spindle-shaped reticular epithelial cells
- Scattered thin-walled vessels
- No significant cytological atypia in this field
- No geographic necrosis or treatment-related fibrosis in this area
This pattern is characteristic of thymic tissue (medullary differentiation), consistent with a teratomatous component showing thymic differentiation within the ovarian mass.
Slide B (IMG_1524) - Key Findings:
A completely different morphology - a diffuse, sheet-like proliferation of small round blue cells with:
- High nuclear-to-cytoplasmic ratio
- Hyperchromatic, coarse chromatin
- Nuclear molding in closely packed areas
- Sparse, delicate fibrovascular stroma (no desmoplasia)
- Brisk mitotic activity and apoptotic bodies/karyorrhexis
- Discohesive growth pattern
- No glandular or squamous differentiation
Integrated Diagnosis
The two slides together represent a mature cystic teratoma (dermoid cyst) with malignant transformation showing two distinct components:
| Feature | Slide A | Slide B |
|---|---|---|
| Pattern | Thymic tissue with Hassall's corpuscles | Small round blue cell tumor |
| Architecture | Biphasic (epithelial + lymphocytic) | Diffuse sheet-like |
| Differentiation | Mature thymic medullary tissue | Primitive/undifferentiated |
| Significance | Teratomatous mature component | Malignant component |
Most likely overall diagnosis:
Immature Teratoma or Mature Cystic Teratoma with Malignant Transformation
The Slide B component raises a differential of:
- Malignant transformation into a neuroendocrine/small cell carcinoma arising from the teratoma - most common malignant transformation in MCT after squamous cell carcinoma
- Primitive neuroectodermal tumor (PNET) arising within the teratoma
- Lymphoma (less likely given the clinical context of primary ovarian mass)
- Desmoplastic small round cell tumor (DSRCT) - to consider given peritoneal spread, but the stroma here lacks the classic desmoplasia
The presence of Hassall's corpuscles (Slide A) in an ovarian tumor is pathognomonic for:
- Thymic tissue within a mature cystic teratoma - a well-documented but rare component of dermoid cysts
- This is an important clue that the entire mass originated as a teratoma with thymic ectopic tissue
Critical Ancillary Studies Recommended (IHC Panel)
| Marker | Rationale |
|---|---|
| CD3, CD20, TdT | To confirm lymphoid component nature; TdT+ suggests lymphoblastic lymphoma |
| CD99 (MIC2), FLI-1, EWSR1 FISH | If PNET/Ewing suspected |
| Synaptophysin, Chromogranin, CD56 | For neuroendocrine/small cell carcinoma |
| p40/p63, CK5/6 | Squamous/epithelial origin |
| WT1, EWSR1-WT1 fusion | If DSRCT considered |
| OCT3/4, SALL4 | Germ cell origin |
| Cytokeratin (AE1/AE3, CAM5.2) | General epithelial marker |
| CD5, CD117 (c-Kit) | Thymoma markers (Slide A component) |
Clinical Correlation
This case is consistent with a malignant germ cell tumor (likely immature teratoma grade 2-3, or mature teratoma with malignant transformation) in a 48-year-old female, presenting with:
- Large multiloculated left adnexal mass (25x20x17 cm post-NACT)
- Bilateral adnexal involvement and Pouch of Douglas deposits
- Prior Trucut biopsy read as "malignant epithelial neoplasm" - this likely sampled the epithelial/thymoid component or a carcinomatous area
- Persistence despite NACT suggests partial chemoresistance, which is more typical of mature MCT with malignant transformation (especially squamous carcinoma arising in dermoid) than of pure high-grade serous carcinoma
The Hassall's corpuscles on Slide A are the key diagnostic clue confirming the teratomatous origin of this entire neoplasm. Thymic tissue in ovarian teratomas is rare but well-established; it can occasionally give rise to a primary ovarian thymoma-like neoplasm. IHC characterization of the Slide B component is essential for definitive classification and prognostication.
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