Results :
We present here the clinicopathologic details of the 3 cases (see Table 1 for summary). Biallelic mutations in the DICER1 gene on exon 11, was detected in all 3 tumors. Germline testing was possible only in 1 case.
Clinical features
Case 1
A 12-year-old female presented with headache, vomiting, left hemiparesis and an episode of generalized seizure. Magnetic resonance imaging (MRI) brain (Figure 1a) showed a heterogeneous lesion with postcontrast enhancement in the right fronto-parietal para-falcine region with surrounding edema and midline shift. Imaging revealed no additional findings. History of an aunt who died of recurrent gynecologic malignancy at 39 years was noted. After gross total resection, radiation therapy (59.4Gy in 33 fractions) was administered. Follow-up chest computed tomography (CT) scans showed multiple, small pulmonary nodules (<4mm). Adjuvant chemotherapy with vincristine, doxorubicin and cyclophosphamide (VDC) alternating with cisplatin, etoposide and ifosfamide (PEI) was administered for 10 weeks, followed by vincristine, dactinomycin and cyclophosphamide (VAC) upto 45 weeks. Magnetic resonance imaging (MRI) brain revealed no tumour and positron emission tomography (PET) scan showed few calcified FDG non-avid nodules at the end of therapy. The child’s current surveillance protocol includes 6 monthly CT chest and ultrasound (USG) pelvis and 2 yearly USG thyroid. She remains in remission after 3 years.
Case 2
A 16-year-old girl presented with abdominal pain and decreased appetite. An emergency laparotomy revealed a necrotic mass based in the broad ligament, involving both adnexae, pouch of Douglas with extensive omental and peritoneal deposits (Fig. 1b). Residual tumour responded well to adjuvant chemotherapy with VDC alternating with PEI (6 cycles) (Fig. 1c). Following chemotherapy, a debulking procedure included left salpingo-oophorectomy, total omentectomy and excision of peritoneal deposits. The patient is on maintenance chemotherapy with vinorelbine and cyclophosphamide and is doing well 6 months post-surgery. No significant family history was noted.
Case 3
A five-month-old female presented with a mass protruding into vaginal introitus. Imaging revealed no other lesion. The initial biopsy was reported as an embryonal rhabdomyosarcoma.
The patient was treated with chemotherapy as per the RMS 2005 EpSSG protocol including ifosfamide, vincristine and dactinomycin. Interim assessment after 4 months suggested suboptimal response. She received second line chemotherapy including doxorubicin and carboplatin for 6 months. Reassessment MRI showed a small vaginal nodule with fibrotic signal (Fig. 1d). The parents refused local treatment with radiotherapy and she was followed with imaging-based surveillance. After 6 months a 2 cm mass extruding into vagina was seen. Repeat scans showed a large recurrent tumour (Fig. 1e, f) with retroperitoneal lymph nodes and mural nodules in the colon. Chemotherapy was commenced with vincristine, irinotecan and temozolomide, however further progression prompted initiation of salvage chemotherapy with PEI alternating with VDC. Despite good response, the parents refused further surgery or radiotherapy. Family history was not contributory, and the family did not consent to germline testing. She had massive progression of disease and was lost to follow-up 2.5 years from presentation.
Pathologic findings :
Case 1
Both resections showed sheets of small round to spindled primitive blastemal cells, with condensed chromatin and small nucleoli. Nodules of immature cartilage were seen to arise abruptly, in the midst of blastemal cells (Fig. 2a-f). Some foci showed alternating hyper and hypocellular spindle cells foci with larger vesicular nuclei and prominent nucleoli (Fig. 2d). Brisk mitoses and apoptosis is noted in both blastemal and sarcomatous foci.
Immunohistochemistry (IHC) with desmin, myogenin, myoD1 and CD99 showed patchy but strong staining in the spindle cell component, while GFAP, smooth muscle actin, synaptophysin and NSE were negative. INI1 was retained in the tumour cells. S100 stained the chondroid elements but was negative in the spindle cell component. Ki 67 proliferation index was >90%.
Case 2
Grossly, the tumour was a single solid-cystic mass measuring 10.0 x 5.5 cm, with multiple irregular, friable projections. On microscopy, alternating sheets and ribbons/trabeculae of densely packed primitive blastemal, monotonous small, round to spindle shaped cells, were separated by hypocellular areas of small spindle cells in collagenized to loose, myxoid stroma (Fig. 3a-f). Areas of perivascular tumour cells, condensation, microcystic foci and cambium-like concentration below pseudocystic spaces were noted (Fig. 3b, 3c). Sarcomatous overgrowth of large spindle cells with abundant clear to eosinophilic cytoplasm, coarse chromatin and prominent nucleoli was present (Fig 3e-f). Brisk mitoses (18-20 per 10 high power fields) including atypical forms and necrosis were identified. Focal immature cartilage was identified in 1 slide (Fig. 3a). The tumour showed a prominent vascular pattern with large dilated blood vessels with thin wall.
Immunohistochemically tumour cells were diffusely positive for desmin and myogenin. There was patchy positivity for myoD1, while AFP, SALL4, CD30, CK, inhibin, PAX8 and WT-1 were negative. INI1 was retained. Cytogenetic studies for PAX-3 or FOXO1 rearrangements were negative.
Case 3
The initial biopsy of the tumour showed multiple tumour fragments lined by squamous epithelium (Fig. 4a-f). A largely hypocellular pattern with small, bland spindle or stellate cells resided in a myxoid background with an immature mesenchymal appearance with focal hypercellular areas and perivascular condensation by smaller, angulated cells. These cells also showed subepithelial concentration, forming a cambium-like layer (Fig. 4b). Also noted were larger blastemal cells with coarse nuclear chromatin and prominent nucleoli, arranged in nests, cords and rosette formations, with a granular pink neuropil-like background (Fig. 4e). Sarcomatous areas composed of nests of larger cells with vesicular nuclei, prominent nucleoli and moderate clear cytoplasm, were also noted (Fig. 4f). Mitotic figures were brisk and more frequent in these foci, along with prominent apoptosis. Cartilage was not identified.
On IHC, myoid markers – desmin (Fig. 4b; inset), myogenin, and myoD1 showed patchy positivity in the small, spindle shaped cells, while the larger blastic cells in cords, nests and rosettes were non-reactive. Both components of the tumour are negative for cytokeratin (AE1/AE3), inhibin, SALL4, synaptophysin and CD99.
The second biopsy of the small residual nodule, showed hypocellular tissue with scattered, bland, spindled to stellate cells, in a loose collagenous background. Few of the spindle cells were desmin positive. No blastemal cells were identified in this biopsy. (Fig. 4g)
The third biopsy of the recurrent tumour, revealed sarcomatous overgrowth, comprising of sheets and nests of round to spindle shaped large cells, with coarse chromatin and abundant mitoses and apoptosis. These cells were morphologically similar to the large blastic cells in cords and nests in the initial biopsy but showed greater degree of anaplasia. (Fig. 4h, i) On IHC, the cells showed no rhabdomyoblastic differentiation, being negative for desmin, myoD1 and myogenin. The tumour cells were diffusely positive for CD99 and SALL4 (Figure 3i; inset), focally positive for synaptophysin and neuron specific enolase (NSE). The tumour cells were negative for chromogranin, cytokeratin (AE1/AE3), calretinin, inhibin, S100, Oct3/4, CD45 and Tdt. INI1 was retained. FISH for EWSR1 gene rearrangement was negative.