A 71-year-old male presented with a history of an asymptomatic raised lesion on the leg for approximately 6 months. On examination, a solitary, 0.5 × 0.4 cm2 sized, round, skin-colored to a pearly-white, soft, shiny papule was noted over the anterior aspect of the right leg [Figure 1]. No other relevant personal or family history was elicited. Dermoscopy (DermLite DL4, 3 Gen, San Juan Capistrano, California, USA, ×10, polarized noncontact mode) revealed a few relatively, well-focused, vessels with multiple morphologies (dotted, linear curved, and linear vessels with branches) in an unspecific distribution, shiny white structures (lines, globules, and structureless areas) were seen on polarized mode over a diffuse yellow structureless area with surrounding brown pigmentation [Figure 2]. Patchy white and brown scales were also appreciated. An excisional biopsy of the lesion was performed with a differential diagnosis of hidradenoma, hidrocystoma, epidermal inclusion cyst, and focal cutaneous mucinosis. Biopsy showed epidermal atrophy, increased dermal mucin causing the splaying of dermal collagen, scattered fibroblasts, and mild perivascular lymphocytic infiltration [Figure 3a and b]. Alcian blue staining was positive for dermal mucin [Figure 3c]. A final diagnosis of solitary cutaneous focal mucinosis (SCFM) was made.
Figure 1.
A single, round, skin-colored to pearly-white papule over the anterior aspect of the right leg
Figure 2.
(a) Vessels of multiple morphologies, shiny white structures (black arrow) over a diffuse yellow structureless area with surrounding brown pigmentation (black asterisk) (b) Well-focused dotted (black arrow), linear curved (red arrow), and linear vessels with branches (blue arrow) seen in an unspecific distribution pattern (DermLite DL4, 3 Gen, San Juan Capistrano, California, USA, noncontact polarized mode, 10x magnification, images capture with DermLite adapter for iPhone 11)
Figure 3.
(a) Thinned-out atrophic epidermis and dome-shaped space oriented horizontally in the upper part of the dermis (H and E, 4×) (b) Increased dermal mucin causing the splaying of dermal collagen, scattered fibroblasts, and mild perivascular lymphocytic infiltration (H and E, 40×) (c) Alcian blue stain showing positivity for abundant dermal mucin (Alcian blue, 40×)
SCFM is a type of primary cutaneous mucinosis characterized by increased dermal deposition of mucin. It is rarely diagnosed clinically owing to its variable clinical presentation.[1] To the best of our knowledge, dermoscopy of SCFM has been described in only one report,[2] with a nonspecific homogenous whitish pattern and a sharply demarcated yellow border as the predominant findings. In the present report of dermoscopy of SCFM, first, from the Indian subcontinent, vessels of multiple morphologies were also noticed, which is contingent upon the technique and pressure applied during dermoscopy. Upon histopathological correlation, diffuse yellow structureless areas and yellow-white lines could be correlated with dense dermal deposition of mucin having birefringent properties and the resulting dermal splaying of collagen, respectively. The surrounding pigmentation can be attributed to the skin phenotype of the patient (Fitzpatrick skin type V). Table 1 summarizes the dermoscopy of SCFM and its differentials. Dermoscopy can aid as a valuable aid in the diagnosis of solitary nodules on the skin.
Table 1.
Dermoscopy of solitary cutaneous focal mucinosis and its differentials
| Disorder | Clinical features typical of the disorder | Dermoscopic finding | Histologic correlates |
|---|---|---|---|
| Nodular hidradenoma (NH)[3] | Uncommon, benign, adnexal tumor, usually presenting as a solitary, asymptomatic, nodule, or cystic lesion of variable color, over head and neck or trunk, most often in middle-aged to the elderly population, with slight female predominance. Spontaneous serous or hemorrhagic discharge may be present | Homogenous area (bluish, less commonly brownish in pigmented lesions, pinkish colored in nonpigmented) | Dermal lobulated masses cells with various-sized ducts, cystic spaces. Increased melanin. Hemorrhage, or Tyndall phenomenon |
| Polymorphic atypical vessels | Vascular nature of NH | ||
| White structures | Fibrovascular or hyalinized stroma | ||
| Epidermal inclusion cyst[4] | Most common, cutaneous cyst presenting as nodules with punctum over the face, neck, or trunk, usually in 20 s to 40 s, involving males twice more commonly than females | Ivory-white background | Underlying keratin mass |
| Punctum | Plugged pilosebaceous unit | ||
| Blue-white veil | Hypergranulosis | ||
| Ruptured epidermal cyst showing red lacunae, peripheral linear branched vessels | Red blood cell components due to bleeding, proliferation of vessels after rupture of the cyst | ||
| Hidrocystoma[5] | Benign cystic tumors of sweat glands presenting as asymptomatic, translucent, skin-colored to blue-black, dome-shaped, nodule with a smooth surface, most commonly localized on the face in middle-aged patients with an equal sex incidence. | Homogenous pink to bluish area, linear vessels with branches | Large unilocular or multilocular cystic space situated within the dermis - |
| Bluish discoloration | Lipofuscin, melanin, or iron in the cyst, or Tyndall phenomenon | ||
| White structures | Changes in the orientation of collagen due to the pressure of the large dermal cysts | ||
| Present case of SCFM | Typically presents as asymptomatic, solitary, flesh-colored or white or red papule or nodule, usually over upper extremities, though any site or oral mucosa can be involved. Tends to involve adults with the age range of 29 to 60, with a slight male predominance. | Diffuse yellow structureless area | Dense dermal deposition of mucin having birefringent properties |
| Shiny white structures (lines, streaks, globules, and structureless areas) | Dermal splaying of collagen | ||
| Surrounding zone of pigmentation | Skin phenotype of the patient (Fitzpatrick skin type V) | ||
| Vessels (Dotted, linear curved, and linear vessels with branches) | Upward displacement of vessels by underlying dermal deposition of mucin |
SCFM=solitary cutaneous focal mucinosis
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Acknowledgements
We would sincerely like to thank Dr. Kavana Soni, Senior Consultant, Lal PathLabs, for her contribution to the case.
References
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