Ram's Horn Nail - Giant Onychomatricoma Treated by Complete Surgical Excision- A Rare Case Report.

Giant onychomatricoma is a rare fibroepithelial nail matrix tumor with only two previous reports in literature, from Mexico. An 80-year-old female patient presented with a progressively painless mass in the left great toe nail, following trauma, of 2 years duration. On examination there was a single, hard, immobile mass of size 4 × 3 × 2 cm with proximal hyperpigmentation of the left great toe nail. The mass was totally excised and a punch biopsy of nail matrix was taken. Histopathology revealed hyperkeratosis, acanthosis, multiple channels lined by flattened epithelium and fibrocollagenous tissue in horizontal orientation in deeper layers. The patient had no recurrence after 1 month. We report this case for its rare and distinct clinical presentation, characteristic histopathology and easy surgical treatment.

What was known?

Onychomatricoma is a fibroepithelial nail matrix tumor which is characterized by brownish nail thickening confined within the nail plate following previous trauma.

Introduction

Onychomatricoma is an extremely rare fibroepithelial nail matrix tumor which has specific clinical characteristics.[1] It commonly occurs following trauma or fungal infection of the nail.[2] It usually presents as localized or diffuse thickening of the nail plate.[3] Giant onychomatricoma is a relatively rare variant with only two cases from Mexico being described worldwide.[4] We report a 80-year-old female patient with giant onychomatricoma treated successfully with complete surgical excision.

Case Report

An 80-year-old female patient presented with complaints of a painless growth in the left great toe nail since 2 years. There was history of trauma to the nail by a blunt object a few months before onset of the mass. Over the past 1 year, the patient used a pen-knife to cut off part of the nail, at least on three separate occasions. Cutaneous examination revealed a single, dirty brown, hyperkeratotic mass of size 4 × 3 × 2 cm arising from the proximal nail fold extending to hyponychium, destroying and replacing the entire nail plate [Figures 1 and 2]. The surface showed linear grooves. There were no splinter hemorrhages. The mass was stony hard in consistency, immobile and fixed to the nail bed. The proximal nail fold showed a hard, non-tender swelling. X-ray of the left foot did not reveal any abnormality.

Figure 1

Large, dirty brown, keratotic mass replacing the left great toe nail

Figure 2

Excised gross specimen of growth from the left great toe nail

The mass was excised and sent for histopathological examination along with a proximal nail matrix biopsy. Histopathologically, this tumor showed hyperkeratosis, acanthosis and marked hyperplasia. The admixed portion show thickened nail plate with multiple channels lined by the keratogenous portion of the nail matrix epithelium characteristic of onychomatricoma [Figures 3, 4 and 5]. There was fibrocollagenous tissue in horizontal orientation seen in deep layer. There was no recurrence 1 week after surgery. The patient was later lost to follow up.

Figure 3

Histopathology of the nail matrix shows multiple channels and keratin pearls (H and E, ×40)

Figure 4

Channels in the matrix lined by a single layer of flattened cells (H and E, ×100)

Figure 5

Histopathology of the nail matrix shows finger-like digitate projections (H and E, ×40)

Discussion

Onychomatricoma belongs to the group of benign tumors arising from nail matrix.[5] Baran and Kint in 1992 first described onychomatricoma and confirmed the nail matrix origin of the tumor.[2] Onychomatricoma has a female to male sex predilection of 2.16:1. The mean age of presentation is 51 years.[2] Onset is usually precipitated by fungal infection or trauma; in our patient, it was precipitated by trauma.

It is characterized by four clinical features; (a) yellowish discoloration of the longitudinal segment of the nail plate of variable width along with small splinter hemorrhages within the proximal portion of the nail, (b) prominent ridging of the nail plate, (c) transverse overcurvature of the nail plate which is more pronounced when the yellowish discoloration is extensive, (d) exposure of filliform tumor of the nail matrix following nail plate avulsion.[1] Our patient had the first three features and the whole nail plate was replaced by the tumor mass. Histopathologically, onychomatricoma has a two-layered stroma with a collagenous and fibroblastic superficial coat and a deep core with less cellularity and thicker collagen along with a V-shaped hyperkeratogenous zone.[2]

The differential diagnosis of onychomatricoma includes amelanotic melanoma, onycholemmal horn, fibrokeratoma and keratoacanthoma of the nail. Amelanotic melanoma is a exophytic, ulcerative, bleeding growth with erosion of the nail plate and histologically characterized by sheets of large tumor cells with moderate cytoplasm and nucleolus.[6] Onycholemmal horn clinically has warty appearance and histologically consists of epithelial proliferation with keratinocytes enlarging towards the surface and producing large amounts of keratin. Fibrokeratoma is histologically characterized by a dense core of longitudinally arranged collagen and complete lack of elastic fibers.[6] Keratoacanthoma is a fast growing, painful lesion usually arising from the hyponychium or the lateral nail groove. Histopathologically marked lateral lip and keratin filled crater are characteristic.[6]

Most reports of onychomatricoma are of localized thickening of plate or yellowish discoloration. In our patient, the whole nail plate was replaced by the growth. The tumor was large and resembled a ram's horn. There is only a single similar report of giant onychomatricoma from Mexico,[4] but the size of the tumor is unknown. Our patient gave history of repeatedly cutting off part of the growth. The recurrent trauma could be responsible for the tumor growing to a huge size. A similar cause was observed by the authors of the previous reported case of giant onychomatricoma. We report this case to highlight the importance of complete surgical excision in the management of this rare condition and the danger of partial excision resulting in a giant growth.

What is new?

We are reporting a case of largest nail matrix tumor in India which measures about 4 × 3 × 2 cm. The large size is probably due to the stimulus given by repeated trauma.