Pigmented Multinucleate Cell Angiohistiocytoma: Not So Infrequent?

Abstract

To the Editor: In 2022, we described the first case of pigmented multinucleate cell angiohistiocytoma (MCAH), demonstrating that the pigment showed positivity with the Masson–-Fontana histochemical technique, while being negative with iron technique.1 At this time, no additional cases of this pigmented variant have been published. However, we have recently identified a second case of pigmented MCAH with similar staining characteristics by histochemical studies. The patient is a 58-year-old woman with a 3-year history of lesions on the back of her hands. The lesions were asymptomatic, although they had gradually increased in number and size. At the time of consultation, the patient had a total of 10 lesions, and a biopsy was performed on the largest lesion (5 mm in diameter). The histopathological study demonstrated a typical case of MCAH (Fig. 1A) with dermal fibrosis, numerous vessels, and polygonal multinucleated histiocytes (Fig. 1B) expressing CD68 (Fig. 1C), CD10, and FXIIIa. Some of the histiocytes showed cytoplasmic brownish pigment (Fig. 2A). This pigment did not stain with the Perls iron histochemical technique (Fig. 2B), but showed strong staining with Fontana-Masson (Fig. 2C), consistent with melanin.FIGURE 1.: A, Multinucleated cell angiohistiocytoma. At this magnification, the lesion appears as a conventional MCAH, with dermal fibrosis, prominent vasculature, and perivascular histiocytic infiltrate (Hematoxylin–-eosin ×40x). B, Some of the histiocytes exhibit angular polygonal conformation (Hematoxylin–-eosin ×20x). C, Expression of CD68 by the histiocytic component of the lesion (×100x).FIGURE 2.: A, Some of the histiocytic cells in the tumor contain brownish cytoplasmic pigment (Hematoxylin–-eosin ×400x). B, The pigment did not stain with the iron histochemical technique (×100x). C, The pigment was positive with the Fontana–-Masson technique (×200x).This finding of a second case in just over a year since the publication of the first one makes us think that, given the low frequency of this entity, the pigmented variant of MCAH may not be so exceptional. It is possible that the amount of pigment varies from case to case and that, therefore, many cases with mild amounts of pigment likely go unnoticed or are diagnosed without being published. Although in the discussion of our first case, we stated that the pigment was consistent with melanin, lipofuscin also stains with the Masson–-Fontana technique. Lipofuscin is a brownish lipid pigment that is considered a “"wear and tear”" or “"cellular aging”" pigment, because it is thought to result from the peroxidation of polyunsaturated lipids in subcellular membranes by free radicals. It is generally observed in cells with intense oxidative enzyme activity.2 In ultrastructural studies, lipofuscin deposits appear as cytoplasmic granules of varying sizes.3 Regarding this, we have performed additional techniques in both cases, including periodic acid-Schiff (PAS), Ziehl–-Neelsen, and Sudan black, which also stain lipofuscin.4 We have also examined the biopsy with an immunofluorescence microscope, becauseas it is known that lipofuscin shows autofluorescence. The pigment in both cases was negative by PAS staining, did not stain with Ziehl–-Neelsen, and did not show autofluorescence. Thus, it does not exhibit the staining or microscopic properties of lipofuscin. On the contraryHowever, both cases present properties consistent with melanin. We have not found any more cases published in the literature. There is a series of sclerosing hemangiomas from 1943, but the drawings of the microscopic observations suggest that they are lesions very different from MCAH.5 Additionally, the pigment demonstrated in some of the cases in that series was clearly identified as iron by its histochemical properties.5