Cutaneous metastasis in a case of Wilm's tumor diagnosed on cytology ‐ A rare case report

A 12‐year‐old male child presented with complaints of a slow growing swelling in the right parasternal region noticed since one month. On examination, the lump was 2 × 2 cm firm, mobile nontender located in the subcutaneous plane which was also confirmed radiologically. Fine needle aspiration cytology was attempted showed small to medium sized monotonous round cell morphology, nuclear molding and mitotic figures were frequent. Few cells exhibiting rosettoid arrangement. No definite epithelial or mesenchymal component was evident. No glio‐fibrillary matrix or lymphoglandular bodies were evident in the smears. Based on morphology, a small round cell tumor was considered with possibilities of Wilm's tumor and Ewing's family of tumor. Based on morphological differentials ICC was requested, tumor cells were positive for strong nuclear WT1 staining while CK and FLI1 were negative. The cytomorphology along with the ICC confirmed the diagnosis of metastatic wilm's tumor. Seven years back, patient had a history of nephrectomy, which on histopathology was reported as triphasic Wilms tumor with favorable histology. Generally Wilm's tumor recurs within 2 years of diagnosis. Late recurrence in Wilm's tumor is rare with only a handful of case reports. Common sites for metastasis include lung, liver, contralateral kidney. Cutaneous metastasis is very uncommon, early detection of which with helps in therapeutic and prognostic decisions. The interesting aspect of this article is cytological detection of cutaneous metastasis of late recurrence Wilm's tumor, which is extremely rare to occur.