Nevus-cell aggregates in lymph nodes: fine-needle aspiration cytologic findings and resulting diagnostic difficulties

We report a case of nodal nevus present in enlarged lymph nodes with changes of dermatopathic lymphadenopathy sampled by fine-needle aspiration (FNA) cytology prior to clinical evaluation of the patient. This lymph node pathology was established later by lymph node excisional biopsy, by which along with a skin biopsy the dermatopathic lymphadenopathy was tentatively attributed to early mycosis fungoides. The FNA revealed fairly atypical melanotic tissue from the dermatopathic lymphadenopathy along with nodules of uniform melanocytic nevoid cells, the presence of which in combination with the dermatopathic atypical tissue provided a tentative diagnosis of metastatic melanoma of unknown primary, with the diagnosis of nodal nevus presented as a less likely possibility. This is to our knowledge the first cytologic report on FNA of nodal nevus, which besides presenting cytologic findings of this entity highlights some of the problems related to providing an accurate diagnosis, if this exceptionally unusual pathologic entity is encountered in lymph nodes sampled for enlargement from pathologies unrelated to this entity. The subject of nevus changes in lymph nodes is briefly discussed.