What is This Black Umbilical Nodule?
A 68-year-old woman with a history of breast cancer presented with a black nodular lesion in her umbilicus that had been present since her teenage years. The umbilical mass had become larger and she was very anxious about it possibly being another malignancy. Cutaneous examination revealed a black, plaque-like nodule within her umbilicus (Figure 1). She also had numerous plaques consistent with seborrheic keratoses on her torso.
What is your diagnosis?
An omphalolith – also referred to as an omphalith, omphalokeratolith or umbolith – is a keratin- and sebum-containing stone-like mass found in the umbilicus.1,2 Very few reports of omphaloliths are present in the literature. The development of these masses correlates to poor hygiene and may involve chronic sebum and keratin deposition in the umbilicus that oxidizes into a solid, black accretion.2-4 This is usually not bothersome unless the mass becomes infected, inflamed or ulcerated.3
Patients usually present with a black stone-like nodule embedded within the umbilicus (Figure 1). However, one report describes the mass as raspberry-like in shape and color.3 Due to the resemblance to an umbilical malignant melanoma, patients such as ours may present with concerns of skin cancer.
Omphaloliths are generally asymptomatic and may go unnoticed for years until inflammation, infection, abscesses or ulceration occurs.3 Patients with these complications complain of associated pain and umbilical discharge.5 One patient, a 26-year-old man, presented with two omphaloliths that eroded into his peritoneal cavity, resulting in peritonitis.5 Another patient, also a 26-year-old man, presented with an omphalolith that subsequently caused a pyogenic granuloma to develop within the umbilicus.6
Histologic examination of an omphalolith shows laminated keratin and sebum. This may be accompanied by hairs and scattered bacteria. The characteristic black color is attributed to melanin and lipid oxidation.2,5,7 Microscopic examination of an umbilical skin biopsy may show granuloma formation with a mixed inflammatory infiltrate.3 A magnetic resonance image from a 33-year-old man described the in situ omphalolith as a well-defined hyperdense signal on both T1- and T2-weighted images.1
The differential diagnosis of a mass in the umbilicus is listed in Table 1.1-3,5,6 Like our patient, individuals may be concerned about the possibility of a primary or metastatic malignancy. A 65-year-old man presented with a new umbilical mass. He underwent a colonoscopy for a suspected Sister Mary Joseph nodule that had metastasized from a primary gastrointestinal malignancy. However, when the mass was removed, its hardened, debris-like features were consistent with an omphalolith.2
Cohen et al described another foreign body-associated umbilical mass in an 18-year-old man with a history of recurrent umbilical infections. It was only composed of terminal hairs and was termed a trichobezoar or belly button bezoar. The composition of the trichobezoar permits it to be differentiated from an omphalolith, which is typically composed of sebum and keratin (in addition to occasionally containing hair).8
The pathogenesis for an omphalolith is still not clearly understood. For many individuals, a direct relationship to personal hygiene has been shown: omphaloliths occur in people who are neglectful about cleaning, or are unable to clean, their umbilicus regularly.1 One hypothesis is that sebum and keratin accumulate over time. Chronic evaporation of residual moisture after sweating or bathing results in the gradual formation of a hard, stone-like calculus.2-4
A deeply retracted umbilicus increases the likelihood of omphalolith formation. This is more common in obese persons. In most of these individuals, the umbilical nodule is black in color and is composed of trapped, desquamated epithelium.
The treatment of an omphalolith is removal of the stone. This can be done via dilation of the umbilicus under local periumbilical anesthesia and subsequent extraction.4 Friedman and Liles described a procedure in which an omphalolith may be easily removed with a warmed otic glycerin preparation (Ceruminex) that is usually used for the removal of cerumen.7 In their report, a 10x10x6 millimeter (mm) omphalolith was extracted by applying Ceruminex for 15 minutes followed by gentle manipulation with a 4-0 curette. The procedure was convenient and painless.7
In patients with multiple episodes of infection, excision of the umbilicus may be done to prevent recurrence.4,9 Upon extraction, the mass may have a moist, white underside and/or a putrid odor.2
An omphalolith is a stone-like umbilical mass made of keratin and sebum. Patients usually present with a hard black nodule that may mimic a melanoma in appearance. Omphaloliths often go unnoticed for many years until abscesses, infection, inflammation or ulceration occur. Histology usually confirms the diagnosis. Omphaloliths originate as accumulations of sebum and keratin; they are frequently associated with poor hygiene and a deep umbilical well. They evolve into hard calculi following exposure to air and subsequent evaporation of residual moisture. Treatment includes removal of the lesion and adequate hygiene to prevent recurrence.
The asymptomatic omphalolith of our 68-year-old patient was removed with a cotton-tipped applicator, which resulted in clinical resolution. When removed, the omphalolith appeared as a black nodule with an underlying moist white surface (Figure 2, left). There was a minor amount of residual erythema in her umbilicus after the omphalolith had been removed (Figure 3, right), but this resolved over time. The patient diligently cleans her umbilicus every day and has not had any recurrence of her omphalolith.
Joseph R. Kallini, MD, is with Eisenhower Medical Center in Rancho Mirage, California and has recently graduated from Baylor College of Medicine in Houston, Texas..
Philip R. Cohen, MD, is with the University of Houston Health Center, University of Houston, Houston, Texas; the Department of Dermatology, University of Texas Medical School at Houston, Houston, Texas; the Department of Dermatology, the University of Texas MD Anderson Cancer Center, Houston, Texas; and the Division of Dermatology, University of California San Diego, San Diego, CA.
Dr. Khachemoune, the Section Editor of Derm DX, is with the Department of Dermatology at the State University of New York Downstate in Brooklyn, NY.
Disclosures: The authors have no conflicts of interest to report.
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8. Cohen PR, Robinson FW, Gray JM. Omphalith-associated relapsing umbilical cellulitis: Recurrent omphalitis secondary to a hair-containing belly button bezoar. Cutis. 2010;86(4):199-202.
9. Mann CV. Hernias. Umbilicus and abdominal wall. In: Mann CV, Russell RCG, Williams NS, eds. Bailey & Love’s Short Practice of Surgery. 22nd ed. London: Chapman and Hall; 1995:899.