Salute sign: A nonambiguous histopathological sign in pityriasis rosea.

Sir,

Pityriasis rosea (PR) is a common papulosquamous disorder, characterized by a primary eruption, the herald patch followed by a secondary eruption after 7–14 days.[1] The lesions are characterized by a peripheral collarette of scaling, which is enhanced by dermatoscopy.[2]

The histopathological features of PR were first described by Unna in 1894. Panizon and Block reviewed the histology of 62 patients with PR and proposed four characteristic histological findings, eczematoid pattern (Unna's sign), absence or decrease of granular cell layer (Lowenbach's sign), extravasation of erythrocytes primarily into the papillary dermis and also partly into the epidermis (Sabouraud's sign), and homogenization of the papillary collagen.[3]

The mound of parakeratotic stratum corneum in PR next to or above the spongiotic focus shows separation and elevation from the rest of the stratum corneum on one side, whereas the other side remains attached to the stratum corneum. This parakeratotic scale corresponds to the fine, peripherally attached and centrally detached scales at the edge of the salmon-colored patch/plaque seen in PR, clinically described as the “hanging curtain” sign.[4] This sign is characteristic of PR and can help to differentiate it from other spongiotic dermatoses, especially in atypical cases where the diagnosis is unclear both clinically and histologically [Figure 1].

Figure 1

Histopathology of pityriasis rosea: Mound of parakeratotic stratum corneum above a spongiotic focus showing separation and elevation from the rest of the stratum corneum on one side, whereas the other side remains attached to the stratum corneum. (H and E, ×10)

This has previously been referred to as the teapot spout sign by some authors due to its resemblance to a teapot spout. Other authors refer to it as the teapot lid sign or just simply the teapot sign.[5] This terminology, comparing the angulated parakeratosis to various parts of a teapot can be quite confusing. We observed that the angulated parakeratosis, which is attached at one end and free on the other end closely resembles a “salute.” Hence we recommend an alternative, simple, and more specific descriptive term for the sign—The salute sign [Figure 2].

Figure 2

Silhouette of a saluting man. The saluting hand closely resembles the parakeratotic scale in pityriasis rosea

Parakeratotic mounds similar to those in PR are also seen in subacute eczema, eruptive psoriasis, pityriasis lichenoides chronica, and patch-stage mycosis fungoides. However, in subacute eczema, the mounds have globules of plasma in them and are not elevated from the underlying stratum corneum. In eruptive psoriasis, the mounds are commonly topped by collections of pyknotic neutrophils and are frequently embedded within a thicker, orthokeratotic, laminated stratum corneum. In pityriasis lichenoides chronica, the parakeratotic mounds are small and embedded in orthokeratotic stratum corneum. The parakeratotic mounds in patch-stage mycosis fungoides are, as a rule, much more elongated than those in PR.

Although this sign is characteristic of PR, it may rarely be seen in erythema annulare centrifugum.

We recommend the use of a simpler, more descriptive terminology for the angular parakeratotic scale—the salute sign.

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Conflicts of interest

There are no conflicts of interest.