Pigmented Paget's disease of nipple: A diagnostic challenge on cytology
A 47-year-old female presented with a pigmented plaque over left nipple since 4 months. There was associated bleeding and pruritus. On examination, there was no palpable mass in the underlying breast parenchyma or axillary lymph node enlargement. A clinical diagnosis of eczema was made and cytological study was requested to rule out melanoma. Imprint smears from the eczematous plaque were prepared. The smears showed clusters and singly scattered, pleomorphic malignant epithelial cells exhibiting, hyperchromatic nuclei, with moderate amount of eosinophilic, vacuolated cytoplasm, with dark brown pigment []. Extracellular deposits of such pigment granules were also noted in a hemorrhagic background. A cytological diagnosis of malignancy, possibly malignant melanoma of the nipple with a differential diagnosis of pigmented Paget's disease was made.\nMammography and magnetic resonance imaging (MRI) were performed to rule out any breast mass. Both investigations were negative.\nFollowing this, excision biopsy of the lesion was carried out and subjected for histopathological examination. The gross specimen was an elliptical bit of skin with a blackish elevated lesion measuring 1 × 0.5 × 0.2 cm. The microscopic sections showed epidermal expansion with clusters of large round to ovoid cells with clear to eosinophilic cytoplasm, pleomorphic nuclei, and prominent nucleoli devoid of intercellular bridges []. Such cells were also seen singly within the malpighian layer. Intracytoplasmic melanin pigment granules were noted in many cells and the melanin nature was confirmed by Masson's Fontana stain. Sub-epithelial tissue exhibited lymphocytic infiltration with pigment incontinence; however, tumor infiltration was not seen in the sub-epithelium. A periodic acid-Schiff (PAS) stain was done which was also negative.\nImmunohistochemistry was carried out and showed strong membrane positivity of tumor cells for HER-2/neu and negative for both S-100 and HMB-45 [], thus excluding melanoma. A final diagnosis of Paget's disease of nipple was made. No recurrence was reported after 1-year follow-up.