Scars may become pigmented for a variety of reasons, including the persistence and/or recurrence of an incompletely removed melanocytic nevus. However, development of an intensely hyperpigmented scar not long after a surgical procedure, in the absence of a clear explanation, would be a distinctly uncommon event. We recently encountered such a lesion in an otherwise healthy 20-year-old patient. In this case, the histopathologic findings led to further questioning of the patient and revealed a cause that had not been previously suspected.
Case Report
A 20-year-old woman was seen for evaluation of a lesion on the left lower abdomen. Six weeks earlier, the lesion had been shave excised by an outside physician; pathology results were not initially available. The patient reported that the lesion had quadrupled in size and darkened considerably since the time of the excision. Her grandmother had died of malignant melanoma. She reported that her only medication was birth control pills. On physical examination, there was a 13X8-mm brown-black nodule with discrete but irregular borders (Figure 1). The clinical impression was recurrent nevus in a shave excision scar. However, because of the rapid growth, dark color, and family history of melanoma, there also was concern about the possibility of an atypical nevus or malignant melanoma. Therefore, an elliptical excision was performed. A report of the initial biopsy specimen was received, with the interpretation benign compound nevus.
Results of histopathologic evaluation of the reexcision specimen showed no residual melanocytic lesion. There was a prominent pigmented, cellular scar occupying the superficial to mid dermis in the central portion of the specimen. The pigmented material consisted of refractile, golden brown granules within macrophages and extracellularly, having a resemblance to hemosiderin (Figure 2). These granules stained positively with Perls stain for iron and with Fontana-Masson stain (Figure 3). Fontana-Masson staining was negative when performed after a bleaching procedure that employed potassium permanganate solution at a concentration of 3 g/L.
The staining results suggested the possibility of minocycline-related hyperpigmentation. Subsequent questioning of the patient revealed that she had been taking minocycline 100 mg twice daily during the 2 years prior to her clinic visit.
Comment
Pigmented scars can arise occasionally because of a number of factors. The sites of persistent and/or recurrent nevus are often pigmented. This pigment, confined to the scar, often shows irregular borders and may have a mottled appearance.1 Pigmented scars also are observed in spontaneously regressing malignant melanoma.2 In a related phenomenon called tumoral melanosis, sheets of melanophages may accompany either a regressed melanoma or epithelial neoplasm.3,4 Pigmentation of scars related to hemorrhage also could occur, eg, following postsurgical trauma or in association with clotting abnormalities, though it is difficult to find literature directly addressing this problem. Other reported associations with hyperpigmented scars include leishmaniasis,5 chickenpox,6 burns,7 Addison disease,8 and hemosiderin-related pigmentation in endometriosis arising in cesarean scars.9 Among other agents that cause cutaneous pigmentation and could potentially produce hyperpigmented scars are heavy metals (eg, gold) and drugs such as amiodarone, phenothiazines, and antimalarials.10,11 Biopsy results of oral hyperpigmentation due to long-term antimalarial therapy have shown macrophages that contain melanin and ferric iron,12 findings resembling those reported here. None of these causes was pertinent to our case.
Minocycline first became available for clinical use in 1967. An association between minocycline administration and black discoloration of thyroid gland follicles in animals was reported that same year.13,14 As early as 1972, Velasco et al15 reported a macular pigmentation of the legs in patients receiving minocycline for the treatment of venereal disease. Since that time, there have been a number of reports of minocycline-induced pigmentation of skin and mucous membranes. Journal articles and textbooks usually divide minocycline-related cutaneous pigmentation into 3 major types. The first, type I, is a blue-black pigmentation that develops in areas of inflammation and scar13,16-19; this is the type that we report here. The second, type II, is a blue-gray pigmentation that develops particularly over otherwise normal-appearing skin of the arms, legs, or face.18,20,21 The third, type III, is usually described as a diffuse or generalized "muddy brown" pigmentation,13,22-25 though in one report this type of pigmentation was actually described as dark blue-gray.24 The Table provides a summary of the clinical and histopathologic changes associated with the 3 major types of minocycline pigmentation. Pigmentation of the nails and nail beds also occurs19,26 and has coexisted with diffuse cutaneous and scleral pigmentation.25 A fourth type of pigmentation that is not specific to minocycline results from fixed drug eruption, as described by Chu et al27 and possibly also represented by the case of Tanzi and Hecker.28 Minocycline also has been associated with discoloration of teeth,23 pigmented conjunctival cysts,29 and black galactorrhea,30 as well as pigmentation of internal organs such as cardiac valves.31,32