Answer: Regressed germ cell tumor

Histology: There is a localized area of fibrosis with hemosiderin deposition. Focally there is an area of necrosis with at high magnification ghosts of cells with prominent nucleoli consistent with necrotic seminoma. The surrounding testis shows seminiferous tubules with germ cell aplasia but lacking germ cell neoplasia in-situ. There is no evidence of vasculitis.

Discussion: This case shows many of the classic findings associated with a regressed germ cell tumor. These include: 1) Discrete nodule of fibrous tissue at times stellate in configuration; 2) Surrounding testicular parenchyma often shows atrophy with impaired spermatogenesis and tubular atrophy; and 3) Scar with clusters of hemosiderin laden macrophages with lymphoplasmacytic inflammatory infiltrate. Other features of regression not seen in this case are: 1) Large coarse calcifications within adjacent scarred tubules; and 2) Residual germ cell neoplasia in-situ. This case also highlights the importance of carefully analyzing necrotic foci as there may be identifiable germ cell tumor. This author is aware of one such case misdiagnosed as torsion resulting in a delay in diagnosis and litigation. Despite the necrosis, immunohistochemistry with OCT3/4, CD117, and CD30 may still be useful in classifying the tumor. Torsion typically affects either neonates or teens or young adults and results in a totally necrotic testis from twisting of the cord. Localized infarcts in the testis most commonly result from a medium sized vessel vasculitis which is often restricted to the testis and only occasionally part of a systemic vasculitis.

Reference(s): Miller JS, Lee TK, Epstein JI, Ulbright TM. The utility of microscopic findings and immunohistochemistry in the classification of necrotic testicular tumors. A study of 11 cases. Am J Surg Pathol 2009;33:1293–1298.

Answer: Papillary thyroid carcinoma, columnar cell variant

Description/Discussion:
The tumor consists of a proliferation of papilla and villous structures, with foci of necrosis. The cytologic features of classic papillary thyroid carcinoma are not well developed. Rather, the nuclei are hyperchromatic and pseudostratified, highly reminiscent of colorectal carcinoma. Immunohistochemistry shows that the tumor is diffusely postiive for CDX-2, as well as TTF-1, PAX8, and thyroglobulin (not shown).

The columnar variant of papillary carcinoma occurs in adults, with a wide age range, as 1 or more thyroid nodules, often with evidence of regionally metastastic disease on presentation. While its cells are “tall,” it is distinguished from the tall cell variant of PTC by its characteristically hyperchromatic and pseudostratified tumor nuclei, closely resembling colorectal adenoma/carcinoma. Moreover, the columnar variant is sometimes positive for CDX-2 as seen here, which may result in mistaking it for a metastasis. Helpfully, this variant is consistently positive for the usual markers of PTC, PAX8, TTF-1, and thyroglobulin. The columnar variant of PTC appears to be more aggressive than conventional papillary carcinoma, with higher rates of extrathyroidal extension, metastatic disease, and death (although recent studies indicate that well encapsulated examples may be more indolent).